225058681

Appears in sequences

• Pell numbers: a(0) = 0, a(1) = 1; for n > 1, a(n) = 2*a(n-1) + a(n-2).at n=23A000129
• Numbers k such that 2*k^2 - 1 is a square.at n=11A001653
• Primitive parts of Pell numbers.at n=22A008555
• Denominators of continued fraction convergents to sqrt(8).at n=22A041011
• a(n) is the least natural number m such that the fractional part of m*(2^0.5) is less than 2^(-n).at n=27A058580
• a(n) is the least natural number m such that the fractional part of m*(2^0.5) is less than 2^(-n).at n=28A058580
• Number of 2 X n binary arrays with a path of adjacent 1's from upper left corner to anywhere in right hand column.at n=20A069306
• Expansion of 1/(1 + 2*x - x^2).at n=22A077985
• a(0) = a(1) = 1; thereafter a(2*n+1) = 2*a(2*n) - a(2*n-1), a(2*n) = 4*a(2*n-1) - a(2*n-2).at n=23A079496
• Greedy frac multiples of sqrt(2): a(1)=1, Sum_{n>=0} frac(a(n)*x)=1 at x=sqrt(2).at n=32A079934
• a(0)=0; a(1)=1; a(2n) = 4*Sum_{k=0..n} a(2k-1); a(2n+1) = a(2n) + a(2n-1).at n=23A089499
• Interlaces "2*n^2 - 1 is a square" with NSW numbers.at n=22A104683
• Pythagorean triples of nearly isosceles triangle.at n=32A114336
• a(2n) = A001653(n) (Numbers n such that 2*n^2 - 1 is a square), a(2n+1) = A038725(n+1).at n=22A117719
• a(2n) = A100525(n), a(2n+1) = A001653(n+1); a Pellian-related sequence.at n=21A129346
• a(n) = Product_{k=1..floor((n-1)/2)} (4 + 4*cos(k*Pi/n)^2).at n=23A152118
• Markov numbers that are semiprime.at n=28A182585
• Pell trisection: Pell(3*n+2), n >= 0.at n=7A187362
• a(n) = 2*a(n-1) + a(n-2) for n > 2, a(0) = a(1) = 1, a(2) = 2.at n=23A215928
• a(n) = -2*a(n-1) + a(n-2) for n > 2, with a(0) = a(1) = 1, a(2) = 0.at n=25A215936